The present invention generally relates to reflectors and, more particularly, relates to concave inflatable reflectors for reflecting electromagnetic signals.
Satellite spacecraft often employ large telescopes and antennas that require large concave reflectors for reflecting electromagnetic signals, such as light, infrared (IR) and radio frequency (RF) signals. Reflectors employed on spacecraft generally must be lightweight and compactly storable in a small volume for transportation into space, and then deployable into a desired shape when in orbit. Deployable reflectors exist which include inflatable reflectors and wire frame supported reflectors. Conventional inflatable reflectors typically use the pressure of a gas to fill and, thus, deform a circular membrane having a reflective surface into a desired shape. The pressurized gas is injected into an optically transparent membrane that is deformed into the deployed shape. The transparent membrane generally includes an inner reflective surface that provides the reflectivity. Tension is typically applied radially to the membrane by a rigid ring formed around the circumference of the reflector. The ring is often in the form of a single inflatable toroid. The inflatable membrane reflector typically utilizes an inflatable tube and struts to move the inflatable membrane into position.
Conventional inflatable reflectors exhibit several drawbacks. The electromagnetic signals (e.g., light signals) that are reflected by the inner reflective surface are required to pass through the transparent membrane and the pressurized gas at least twice before reaching a focal optical instrument. The transparent membrane and inflating gas may adversely affect the signals and may cause minute distortions in the optical wavelength of the signals. Additionally, conventional inflatable reflectors are generally sensitive to thermal and vibrational disturbances resulting from very low stiffness of the resultant structure.
Another deployable reflector structure employs a reflective membrane on the rear side of a support structure to create a biconcave reflector. The biconcave reflector has a membrane that exerts a force on the reflective membrane to pull the reflector into a desired shape. This force can either be accomplished mechanically by using springs or by applying a non-contact force produced by a magnetic or electrostatic field. A surrounding inflatable ring may further provide tension to the resultant structure. This biconcave reflector technique eliminates the transparent membrane through which signals would have to pass, however, there exists difficulty in the application of force to the reflector to achieve the desired shape. Further, springs that are used to form the resultant structure create point-like loads and, thus, form dimples on the reflective surface, which can distort the electromagnetic signals. The use of a magnetic or electrostatic field to produce the force can be difficult to create and effectively control.
It is therefore desirable to provide for a deployable reflector for reflecting electromagnetic signals in a lightweight and compact structure that may be easily deployed to a desired shape. It is further desirable to provide for an inflatable reflector that may be easily used for spacecraft applications, and which does not suffer from disadvantages of conventional deployable reflectors.
The present invention provides for an inflatable reflector that is lightweight and compact and can be easily inflated to a desired shape. The inflatable antenna has a plurality of inflatable tori including a first inflatable toroidal member and a second inflatable toroidal member arranged one radially inward of the other. A front membrane is attached to a front side of the plurality of inflatable tori to form a reflective surface, and a rear support membrane is attached to a rear side of the inflatable tori and provides a rear support structure. The reflector is compact and lightweight and the plurality of inflatable tori are inflated by a pressurized gas to deploy the reflector into a desired shape.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.